# Cycas revoluta
**Cycas revoluta** Thunb. (ソテツ, sotetsu), the sago cycad or Japanese sago palm, is a slow-growing evergreen cycad native to coastal [East Asia](https://www.edgepedia.org/east-asia), with a stout trunk and a crown of stiff, dark green, palm-like leaves. Despite its common names it is neither a palm nor a fern; it is a gymnosperm, a seed plant whose seeds are not enclosed in a fruit, related to conifers and Ginkgo.[1](https://www.mnhn.fr/fr/sagou-du-japon) It was first published by the Swedish botanist Carl Peter Thunberg in 1782 and is the accepted name in Kew's Plants of the World Online.[2](https://powo.science.kew.org/taxon/328823-2)
| Key fact | Detail |
|---|---|
| Scientific name | *Cycas revoluta* Thunb., first published 1782 in Verh. Holl. Maatsch. Weetensch. Haarlem 20: 424[2](https://powo.science.kew.org/taxon/328823-2) |
| Native range | China (Fujian), Japan (southern Shikoku, Kyushu, Nansei-shoto) to eastern Taiwan; grows at 0-300 m elevation[2](https://powo.science.kew.org/taxon/328823-2) • [3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/) |
| Size | Trunk to about 4 m (up to 6-7 m in very old plants); leaves 0.5-2 m long[1](https://www.mnhn.fr/fr/sagou-du-japon) • [3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/) |
| Growth rate | Slow; RHS gives 20-50 years to maturity and 1-1.5 m height in UK conditions[4](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details) |
| Toxicity | All parts contain cycasin and other toxins; harmful if eaten and toxic to dogs and cats[1](https://www.mnhn.fr/fr/sagou-du-japon) • [4](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details) |
| Conservation | IUCN Red List status Least Concern, but wild populations now face the invasive cycad aulacaspis scale and sea-level rise[5](https://esj-journals.onlinelibrary.wiley.com/doi/abs/10.1111%2F1442-1984.12505) • [6](https://www.sciencedirect.com/science/article/abs/pii/S0006320726000856) |
| Uses | Ornamental planting worldwide; starch from the trunk processed into "false sago" flour in Japan; leaves used decoratively and liturgically[1](https://www.mnhn.fr/fr/sagou-du-japon) • [7](https://portals.iucn.org/library/sites/library/files/documents/2003-010.pdf) |
## Description
*Cycas revoluta* is a perennial, dioecious plant, meaning male and female reproductive structures occur on separate individuals. It is arborescent, with a robust cylindrical trunk generally about 20 cm in diameter at maturity, covered by the persistent bases of old leaves; in very long-lived plants the trunk can reach 6-7 m, and the MNHN gives about 4 m as a typical maximum.[3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/) • [1](https://www.mnhn.fr/fr/sagou-du-japon) The pinnately compound leaves are grouped in a rosette at the stem tip, dark glossy green, leathery and persistent, 0.5-2 m long, with the leaflet margins curved backward (revolute), the feature that gives the species its name; *revoluta* translates as "rolled back".[3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/) • [1](https://www.mnhn.fr/fr/sagou-du-japon) Young leaves tend to be pubescent and become smooth with age.[3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/)
**Reproduction.** Male plants produce fusiform cones about 60 cm long among the terminal leaves; their scales release pollen dispersed by insects and wind. Female plants instead produce reduced, beige-velvety modified leaves (sporophylls) in the heart of the crown, each bearing 6-8 large ovules on its axis. The fertilized ovule develops into a large, flattened seed protected only by a fleshy red envelope, with no fruit wall around it.[1](https://www.mnhn.fr/fr/sagou-du-japon) • [3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/) Cones are rarely seen except on mature plants, which under cultivation can take decades to reach.[4](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details)
## Distribution and habitat
The native range covers Fujian in southeastern China, southern Shikoku and Kyushu in Japan including the Nansei-shoto (Ryukyu) islands, and eastern Taiwan, in subtropical coastal habitats at 0-300 m elevation.[2](https://powo.science.kew.org/taxon/328823-2) • [3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/) It is the only cycad native to Japan, and in the [Ryukyu Islands](https://www.edgepedia.org/ryukyu-islands) it has been revered for centuries, forming part of the local food, agroecological, and symbolic culture.[5](https://esj-journals.onlinelibrary.wiley.com/doi/abs/10.1111%2F1442-1984.12505) The species has been introduced widely, including to Alabama, the Azores, and Bangladesh, and was recorded in Bermuda as early as 1829.[2](https://powo.science.kew.org/taxon/328823-2) • [8](https://ukotas.info/species/bermuda/cycas-revoluta)
## Taxonomy
Thunberg described the species in 1782, at which point it had already been cultivated in Europe for about 100 years.[5](https://esj-journals.onlinelibrary.wiley.com/doi/abs/10.1111%2F1442-1984.12505) Kew's Plants of the World Online accepts the name and lists six heterotypic synonyms, including *Cycas aurea* (1868), *Cycas miquelii* (1900), and *Epicycas miquelii* (1998).[2](https://powo.science.kew.org/taxon/328823-2) The classification places it in the family [Cycadaceae](https://www.edgepedia.org/cycadaceae), order [Cycadales](https://www.edgepedia.org/cycadales), subclass Cycadidae.[2](https://powo.science.kew.org/taxon/328823-2)
**The Taiwan question.** Populations in Taiwan's Taitung County were recognized in 1994 as a separate species, *Cycas taitungensis*, considered sister to *C. revoluta*. Recent multi-locus genetic comparisons argue for synonymy, treating the Taiwanese populations as a marginal southern population, and current taxonomy places *C. taitungensis* within the concept of *C. revoluta*; Kew lists it as a synonym. This merging has conservation implications, because it would remove the Taiwanese populations' separate endangered Red List status.[9](https://esj-journals.onlinelibrary.wiley.com/doi/10.1111/1442-1984.12494) • [2](https://powo.science.kew.org/taxon/328823-2)
## Toxicity
All parts of the plant are toxic. The principal toxin is cycasin, a glycoside with the formula C₈H₁₆O₇N₂ first isolated from the seeds of Japanese cycad by Kotaro Nishida, Akira Kobayashi, and Tomonori Nagahama in 1955 and identified as glucosyloxyazoxymethane; its aglycone is identical to that of macrozamin from Australian cycads, but its sugar component is glucose rather than primeverose.[10](https://www.jstage.jst.go.jp/article/bbb1924/19/1/19_1_77/_article/-char/en) [Cycasin](https://www.edgepedia.org/cycasin) and its metabolite methylazoxymethanol (MAM) are extracted from cycad seeds and roots; MAM induced liver and renal cell carcinomas in nonhuman primates over a 32-year study by the U.S. [National Cancer Institute](https://www.edgepedia.org/national-cancer-institute). Poisonings typically result from misuse of the seeds as food or as a supposed health agent.[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC4289646/) The plant also contains beta-N-methylamino-L-alanine, a neurotoxic amino acid, and cycasin itself causes gastrointestinal irritation and liver failure.[1](https://www.mnhn.fr/fr/sagou-du-japon) A Taiwanese clinical study of acute *Cycas* seed poisoning documented the cyanogenic potential of the seeds, though measured cyanide levels in the cases did not reach the toxic range.[12](https://pubmed.ncbi.nlm.nih.gov/15083936/) Horticultural guidance accordingly labels the plant harmful if eaten, a skin irritant, and toxic to dogs and cats.[4](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details)
## Uses
The species is grown and sold extensively as an ornamental, prized for its tropical effect and easy care as a specimen or container plant.[3](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/) • [13](https://hort.ifas.ufl.edu/shrubs/cycrev.pdf) In Japan, starch extracted from the stipes yields a flour called "false sago" (faux sagou), which must be washed at length and cooked to eliminate the toxins before it can be eaten.[1](https://www.mnhn.fr/fr/sagou-du-japon) In the French Antilles, the leaves sometimes replace palm and box branches on [Palm Sunday](https://www.edgepedia.org/palm-sunday), giving the plant the nickname "petit rameau".[1](https://www.mnhn.fr/fr/sagou-du-japon) Japan is the principal exporter of cycad leaves, harvested from cultivated plants, for floral arrangements; a 2003 IUCN action plan found no evidence that leaf harvesting harms wild populations, and noted that because *C. revoluta* is widely cultivated there is no need for trade from wild populations.[7](https://portals.iucn.org/library/sites/library/files/documents/2003-010.pdf)
## Cultivation
The plant grows slowly and tolerates pot confinement, making it a standard architectural and container subject.[4](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details) The Royal Horticultural Society recommends growing it under glass in a loam-based, peat-free compost with added leaf mold and grit, in full light with shade from hot sun and moderate humidity, watering moderately in the growing season and sparingly otherwise; in frost-free areas it can grow outdoors in moist but well-drained soil in bright light. It needs an acid or neutral soil and a sheltered, south- or east-facing position, and is rated H3 (hardy in coastal and relatively mild parts of the UK, -5 to 1 °C).[4](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details) The MNHN gives the cold limits more precisely: leaves are damaged from -3 °C and the plant dies from about -10 °C.[1](https://www.mnhn.fr/fr/sagou-du-japon) Propagation is by seed or by suckers, and the plant is generally pest-free outdoors, though susceptible to glasshouse red spider mite under glass.[4](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details)
## Conservation
The IUCN Red List currently rates *Cycas revoluta* as Least Concern.[5](https://esj-journals.onlinelibrary.wiley.com/doi/abs/10.1111%2F1442-1984.12505) Two recent threats have changed the outlook. The cycad aulacaspis scale (*Aulacaspis yasumatsui*), a specialist scale insect inadvertently transported from southeastern Asia within the last three decades, was detected in southern Florida in 1995, where it decimated cultivated cycads, and drove *Cycas micronesica* on Guam from the most abundant forest tree to IUCN-endangered within five years. It has now invaded wild *C. revoluta* populations on Amami-Oshima and Okinawa-jima in Japan, and researchers recommend monitoring and evaluating native predators as biological control agents, since chemical pesticides are expensive, labor-intensive, and unsuitable for wild populations.[5](https://esj-journals.onlinelibrary.wiley.com/doi/abs/10.1111%2F1442-1984.12505) • [14](https://www.cycadgroup.org/wp-content/uploads/2025/03/CAS_biocontrol_CSG.pdf) A genomic study using genome-wide SNP data identified two temperature- and precipitation-structured conservation units across the species' range and found that sea-level rise and the scale invasion add vulnerability beyond that predicted by direct climatic variables alone, posing immediate threats to population persistence.[6](https://www.sciencedirect.com/science/article/abs/pii/S0006320726000856)
## References
1. [Sagou du Japon (*Cycas revoluta*), Muséum national d'Histoire naturelle](https://www.mnhn.fr/fr/sagou-du-japon)
2. [*Cycas revoluta* Thunb., Plants of the World Online, Kew Science](https://powo.science.kew.org/taxon/328823-2)
3. [Cycadaceae, Jardín Botánico Iztacala, UNAM](https://sitios.iztacala.unam.mx/jabiz/cycadaceae/)
4. [*Cycas revoluta* (Japanese sago palm), RHS Plant Profile](https://www.rhs.org.uk/plants/5127/cycas-revoluta/details)
5. [Deloso et al. (2025). Biological invasion by the cycad-specific scale pest *Aulacaspis yasumatsui* into *Cycas revoluta* populations on Amami-Oshima and Okinawa-jima, Japan. Plant Species Biology 40(4): 280-291](https://esj-journals.onlinelibrary.wiley.com/doi/abs/10.1111%2F1442-1984.12505)
6. [Climate change-mediated catastrophe exacerbates genomic vulnerability of a coastal cycad. Biological Conservation 317 (2026)](https://www.sciencedirect.com/science/article/abs/pii/S0006320726000856)
7. [Donaldson, J.S. (2003). Cycads: Status Survey and Conservation Action Plan, IUCN](https://portals.iucn.org/library/sites/library/files/documents/2003-010.pdf)
8. [*Cycas revoluta*, UK Overseas Territories database of Alien Species (Bermuda)](https://ukotas.info/species/bermuda/cycas-revoluta)
9. [Englehardt (2025). Threats to cycad biocultural heritage in the Amami Islands, Japan. Plant Species Biology](https://esj-journals.onlinelibrary.wiley.com/doi/10.1111/1442-1984.12494)
10. [Nishida, Kobayashi & Nagahama (1955). Studies on Cycasin, a New Toxic Glycoside, of *Cycas revoluta* Thunb. Bulletin of the Agricultural Chemical Society of Japan 19(1): 77-84](https://www.jstage.jst.go.jp/article/bbb1924/19/1/19_1_77/_article/-char/en)
11. [Toxic phytochemicals and their potential risks for human cancer, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4289646/)
12. [Acute *Cycas* seed poisoning in Taiwan, PubMed](https://pubmed.ncbi.nlm.nih.gov/15083936/)
13. [*Cycas revoluta*, UF/IFAS Extension Fact Sheet FPS-162](https://hort.ifas.ufl.edu/shrubs/cycrev.pdf)
14. [IUCN/SSC Cycad Specialist Group, Subgroup on Invasive Pests: CAS biocontrol](https://www.cycadgroup.org/wp-content/uploads/2025/03/CAS_biocontrol_CSG.pdf)
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*Topic: Encyclopedia › Life and health › Plants and algae › Seed plants › Conifers and other gymnosperms › Cycads (Cycadales) › Cycads of the genus Cycas (Cycadaceae) › Cycas species of tropical and subtropical Asia*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license